Coolant hoses in vehicles transfer the coolant fluid from the engine to the radiator, and are subject to high heat loads from radiated heat sources, and thus, must withstand high temperatures in service. It is not acceptable for hoses to fail during service, and buyers of vehicles increasingly demand that the original hoses last the entire life of the vehicle, which is often in excess of 200,000 km.
Ethylene/propylene/diene terpolymer (EPDM) rubbers are used to make the majority of coolant hoses for vehicles, and the types of polymers used are often specified in the manufacturers specifications, such as, for example, the Daimler specification DBL6254. This specification describes the required properties of elastomeric compositions before and after aging at specified temperatures. Other elastomeric compositions are disclosed in U.S. Pat. No. 6,047,740; WO 1997/000286; and WO 2011/079207. There is a need for elastomeric compositions with improved retention of mechanical properties and good thermal properties, and which can be used in high temperature applications. This need is met by the following invention.